I use loctite243 on my mounts and action screws. not sure if its right thing to do but not hade one work loose.
never done it , shouldn't be required with quality mounts unless it's a shoulder cannon?
I never used to but after a recent incident with a Tikka 30-06 trigger assembly coming loose and the fact that Tikka triggers are only held in by one cap head bolt I now use loctite on that as I had an accidental discharge due to the trigger assembly being loose, which was not nice!
Regards,
Gixer